Refrigeration systems, such as those found in typical household appliances, often include a frozen food compartment and a fresh food compartment. The two compartments are interconnected by a passageway that is regulated by a damper having a movable (rotatable, slideable, etc.) damper door. When the temperature in the fresh food compartment rises above a predetermined level, the damper is actuated to open the damper door and permit a lower temperature air from the frozen food compartment to pass through the passageway and into the fresh food compartment. When the temperature in the fresh food compartment has dropped to a desired level, actuation of the damper is discontinued, the damper door is closed, and the passageway between the two compartments is blocked.
The dampers can be actuated in a variety of different ways and the damper doors can be driven using a variety of apparatuses and methods. One type of damper that is known in the art is a motorized damper. The motorized damper operates to open the damper door when a voltage signal is supplied to a solenoid or motor operatively coupled by an actuator to the damper door. With the energized solenoid or motor, the damper door can be transitioned from a closed to an open position. Thereafter, when the voltage is removed, the damper is no longer actuated, and a resilient member such as a spring is able to draw the damper door back into the closed position. To ensure that the door opens and closes at the proper times, the refrigeration system having a motorized damper typically includes a sensor that monitors a temperature in the fresh food compartment and a control device that provides the voltage signal to the damper to drive the damper door to an appropriate position based on this sensed temperature in the fresh food compartment.
While this type of damper control provides rapid actuation of the damper door, it is not very energy efficient. If a significant amount of cooling for the fresh food compartment is needed, such as in warm climates when the refrigerator door is opened many times or held open for long periods by children or others, the amount of energy that is wasted opening and closing the damper door can be significant.
Another example of a damper that is known in the art and that does not suffer from the energy usage issues of the previous type is a bellows or refrigerant damper. This type of damper uses a bellows that is filled with a refrigerant. The bellows are positioned in the fresh food compartment. As the refrigerant expands based on an increase in the ambient temperature in the fresh food compartment, the bellows move an actuator that opens the damper door. As the temperature in the fresh food compartment falls, the refrigerant in the bellows contracts or condenses. As this occurs, the bellows contract to allow the damper door to close. A resilient member, such as a spring, may be used to force the damper door to close as the bellows contract.
To provide a more rapid control, some refrigerant dampers have began to incorporate a heater to cause the bellows to expand quicker when the temperature in the fresh food compartment rises above the set point. In such a system, the refrigerant damper is actuated when a voltage is supplied to a heating element that is coiled around the bellows. The supplied voltage causes the heating element to increase the temperature of the refrigerant within the bellows to expand rapidly. As described above, this causes the bellows to expand and the damper door is moved into an open position. When the voltage is removed from the heater, the ambient air in the compartment causes the temperature of the refrigerant to drop. As a result of the cooling refrigerant, the bellows contract or deflate and, like above, a spring is able to resiliently bias the damper door back into the closed position. Such a system is disclosed in U.S. Pat. No. 4,653,283 to Sepso, entitled REFRIGERATOR SYSTEM, CONTROL DEVICE THEREFOR AND METHODS OF MAKING THE SAME, the teachings and disclosure of which are incorporated herein in their entireties by reference thereto.
Unfortunately, while such a damper system described by the '283 patent provides distinct advantages over the ambient temperature controlled bellows-driver damper system, the placement of the heating element around the bellows presents certain inefficiencies. Specifically, because the bellows must be able to expand and contract without obstruction, the heating element that is coiled therearound must be positioned so at to not interfere with this mechanical movement of the bellows. As such, the heating element must be positioned at least a certain distance from the bellows. The heat transfer from the heating element to the damper bellows, therefore, must occur through the ambient, cool air to affect the refrigerant in the bellows. This results in a less than efficient heat transfer, requires more power to provide actuation of the damper, and unnecessarily delays the actuation thereof. Such problems detract from the performance of this type of damper despite advantages in cost savings and quiet, high-force operation over the electrically actuated damper systems that utilize a motor or solenoid.
Thus, a damper system that can be precisely activated and deactivated with the performance provided by a motor or solenoid type actuator and that can provide a low-cost, efficient, quiet, high-force and reliable actuating force such as that provided by a bellows type actuator that overcomes the problems with each is desirable. The invention provides such a damper system. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.